It is known that the wheels of vehicles circulating on the road require frequent balancing operations, consisting in fitting to the wheel rim small balancing weights, made of lead or other material, suitable for offsetting the irregular distribution of weights in the tire.
To perform this operation, balancing machines are commonly used with a horizontal rotating shaft, so-called “balancing shaft”, on which the wheel to be balanced must be placed integral by means of one or more centering and fixing parts.
The measurement of wheel unbalance is determined once the wheel has been rotated on the balancing shaft by means of a series of electronic or electro-mechanical devices, such as force transducers fitted along the balancing shaft.
To the unbalance measurement are normally added other characteristic measurements, such as wheel roundness measurement, wheel eccentricity, amount of tread wear, etc., normally made by means of suitable measuring sensors without contact (laser, ultrasounds or the like), mounted on the machine frame and substantially turned towards the balancing shaft.
Once the necessary measurements have been made, the machine is able to calculate the quantity of the balancing weights to be fitted on the wheel rim to offset the wheel irregularities.
The balancing weights are usually fitted manually by an operator at one or more precise points of the wheel rim chosen by the machine or the operator himself.
The weight fitting operation is not always practical and easy, above all because the balancing weight fitting points are located inside the wheel rim and therefore not well lit.
To overcome this drawback, the operator can use an electric lamp of the type used in workshops with the drawback, however, of having to fit the balancing weights with just one hand, because the other hand must be used to direct the light inside the wheel rim.
Particular types of balancing machines on the other hand have a halogen lamp located roughly underneath the balancing shaft and intended to light up the inner face of the wheel.
The lighting of such halogen lamps however is not perfect and is often partial because the light produced is not diffused in a uniform way and comes from a single point of emission, i.e., the lamp itself.
This therefore determines the splitting up of the rim area into well lit areas and shadow areas.
Another drawback of traditional balancing machines which restricts the practical intervention of the operator in fitting the balancing weights consists in the fact that the operator is not always able to correctly identify the precise point at which to fit the weights, which usually coincides with the position corresponding to “12 o'clock”.
In this respect, it is specified that in this treatise by the expressions “3 o'clock”, “6 o'clock”, “9 o'clock” and “12 o'clock” are meant the relevant angular positions on the wheel perimeter hypothetically split up into twelve hours like the dial of a clock, where “6 o' clock” and “12 o'clock” are therefore defined by the intersection of the wheel with the vertical plane on which the balancing shaft rests, while “3 o'clock” and “9 o'clock” are defined by the intersection of the wheel with the horizontal plane on which the balancing shaft rests.
To identify “12 o'clock” on the wheel, the operator ideally traces the vertical line passing through the balancing shaft and positions the balancing weights by evaluating their position approximately, with the risk of this not being exact.
To overcome this drawback, some balancing machines have a laser pointer mounted on a series of linear and/or angular actuators which allow moving it to direct the light beam towards the exact point of the wheel in which the operator has to fit the balancing weights.
These mobile laser pointers also however have various drawbacks including the fact that they are particularly complex and expensive and that sometimes, despite their presence, the operator, to keep things simple and/or by habit, continues to adopt the balancing weight fitting system at “12 o'clock”.